Initiator and gas generator

ABSTRACT

An initiator includes a header substantially formed of at least one of ceramic and resin, a pair of electrode pins disposed through the header and having extremities facing a front end of the header, a bridge circuit line provided between the extremities of the electrode pins, a reaction agent configured to react upon being heated by the bridge circuit line, and a cup surrounding the reaction agent and a side surface of the header.

BACKGROUND OF THE INVENTION

The present invention relates to an initiator suitable to be built in a gas generator for an airbag apparatus, a seat belt pretensioner, and the like, and a gas generator provided with the initiator.

An airbag apparatus provided in a high-speed movable body such as motor vehicles is configured to inflate a bag-shaped airbag rapidly by a gas generator referred to as an inflator. The gas generator includes a gas generating agent and an initiator to make the gas generating agent initiate gas generating reaction. In the related art, the initiator is provided with a reaction agent, and a filament (bridge wire) as a heating resistor for initiating the reaction of the reaction agent (see e.g., U.S. Pat. No. 5,140,906 (incorporated herein by reference)).

FIG. 6 is a cross-sectional view of an initiator and an igniter (gas generator) provided with the initiator. An igniter 10 is configured to ignite a booster charge 10 b (mixture of titanium metal powder, metal boron powder, and potassium perchlorate) filled in a cap 10 a by the initiator. The initiator includes a metallic cup 12, an annular inner header 16 for sealing the entrance side of the cup 12, parallel conductors 22, 24 disposed in an inner hole 20 of the inner header 16 and sealed by a glass seal 30, an igniting bridge wire 28 bridged between the extremities of the conductors 22, 24, a static electricity charging bridge wire 32 bridged between the conductor 24 and the inner header 16, and an initiator charge (mixture with titanium metal powder, zirconium metal powder, and potassium perchlorate) 18 filled in the cup 12 to be ignited by the bridge wire 28. The glass seal 30 seals between the outer peripheral surfaces of the pin-shaped conductors 22, 24 and the inner peripheral surface of the inner header 16.

In case of emergency such as vehicle collision or the like, a voltage is applied to the bridge wire 28 via the conductors 22, 24. Accordingly, the bridge wire 28 develops a heat, the initiator 18 is ignited, and the reaction starts. By the reaction of the initiator charge 18, high-pressure gas or heat is generated, whereby the booster charge 10 b of the gas generator triggers a gas generating reaction.

When manufacturing the initiator in the related art shown in FIG. 6, the pair of pin-shaped conductors 22, 24 are inserted into the inner hole 20 of the metallic inner header 16. Glass powder is then filled between the outer peripheral surfaces of the conductors 22, 24 and the inner peripheral surface of the inner hole 20, and subsequently, the glass powder is sintered. Therefore, it is necessary to retain the conductors 22, 24 until sintering is completed, which causes a trouble in manufacture and costs much.

SUMMARY OF THE INVENTION

The present invention aims to solve one or more of these and other problems. It is an object of the present invention to provide an initiator which can easily be manufactured and lower the manufacturing cost, and a gas generator using the initiator.

According to an embodiment of the present invention, an initiator is provided. The initiator includes a header formed of ceramic or synthetic resin, a pair of electrode pins disposed through the header with the extremities facing the distal end surface of the header, a bridge circuit line provided between the extremities of the electrode pins, a reaction agent reacting upon being heated by the bridge circuit line, and a cup surrounding the reaction agent and the side surface of the header.

According to alternative embodiments of the invention, the cup may be formed of metal and may be fixed to the header by caulking. An insulating layer may be formed on the inner surface of the cup. Part of one of the electrode pins and the cup may be disposed close to each other via a discharge gap, and static electricity may be discharged via the discharge gap.

A projection may protrude from partway along the length of the electrode pin in the direction toward the cup so that the discharge gap is formed between the projection and the cup.

Part of the header may be metalized and one end of the metalized portion may be in contact with the cup, and the other end thereof may extend to the position close to one of the electrode pins, so that static electricity may be discharged via the discharge gap between the other end and the electrode pin.

A pin-to-pin distance adjusting member may be secured to the extremity of the electrode pin so as to approach the other electrode pin, and the bridge circuit line may be connected to the pin-to-pin distance adjusting member.

The extremities of the respective electrode pins may be bent toward each other.

According to further embodiments of the present invention, gas generators containing various embodiments of the initiator may be provided.

The initiator according to an embodiment of the present invention may employ a header formed of ceramic, and hence a ceramic header with a bridge circuit line can be manufactured, for example, by unitizing the electrode pins with the ceramic mold and then sintering the same, or by inserting the electrode pins into a ceramic sintered body or a synthetic resin mold formed with holes and sealing the same. This manufacturing method is simpler and costs less in comparison with a case in which the electrodes are inserted into the metal inner header and fixed with a glass seal while retaining the same, as in the case of above-described U.S. Pat. No. 5,140,906.

Therefore, according to the present invention, the manufacturing cost of an easy-to-manufacture initiator can be reduced.

In the present invention, it is easier and preferable to form the cup with metal and fix it to the header by caulking.

Further, by providing an insulating layer on the inner surface of the cup, a short circuit between the electrodes via the cup is prevented.

Further, where part of one of the electrode pins and the cup are disposed close to each other via a discharge gap (such as an air gap) so that static electricity can be discharged via the discharge gap, the mechanism of discharging static electricity can be configured easily at a low cost.

Further, a projection may protrude from partway along the length of the electrode pin in a direction toward the cup so that the discharge gap is formed between the projection and the cup.

When part of the header is metalized and one end of the metalized portion is in contact with the cup, and the other end thereof extends to a position close to one of the electrode pins, so that static electricity can be discharged via a discharge gap between the other end and the electrode pins, the mechanism of discharging static electricity can be configured easily at a low cost. Therefore, the need for a bridge wire for discharging static electricity may be eliminated.

According to an embodiment of the present invention, a pin-to-pin distance adjusting member may be secured to the extremity of at least one of the electrode pins so as to approach the other electrode pin, and the bridge circuit line is connected to the pin-to-pin distance adjusting member. In this arrangement, the distance between the pin-to-pin distance adjusting member and the other electrode pin, or the distance between the pin-to-pin distance adjusting members can be reduced so that the length of the bridge circuit line is reduced.

An embodiment of the present invention may employ a configuration in which the extremities of the electrode pins are bent toward each other. In this configuration, the distance between the electrode pins can be reduced, and hence the length of the bridge circuit line can reduced.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below.

FIG. 1 is a cross-sectional view of an initiator according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the initiator according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of the initiator according to further embodiment of the present invention.

FIG. 4(a) is a cross-sectional view of the initiator according to an embodiment of the present invention, and FIG. 4(b) is a perspective view of the pin in FIG. 4(a).

FIG. 5 is a cross-sectional view of an initiator according to another embodiment of the present invention.

FIG. 6 is a cross-sectional view of the igniter having the initiator according to the related art.

FIG. 7 is a cross-sectional view of the initiator according to another embodiment.

FIG. 8 is a cross-sectional view of an airbag device according to an embodiment.

FIG. 9 is a perspective view of a seat belt device according to an embodiment.

DETAILED DESCRIPTION

Referring now to the drawings, an embodiment of the present invention will be described. FIG. 1 to FIG. 4(a) and FIG. 5 are cross-sectional views of an initiator according to the embodiment of the present invention, and FIG. 4(b) is a perspective view of an electrode pin shown in FIG. 4(a).

An initiator 50 in FIG. 1 includes a cup 52 formed of SUS304 or the like and a header 54 formed of ceramic or resin inserted into the entrance of the cup 52, and a reaction agent 48 is filled between the cup 52 and the distal or front end surface of the header 54.

In this embodiment, the header 54 includes a cylindrical front half 58 of small diameter, and a cylindrical rear half 60 of large diameter continuing from the rear end of the front half 58.

The header 54 is formed with a pair of holes 66 through the thickness of the header 54 at the center thereof. Electrode pins (hereinafter, they may simply be referred to as pins) 62, 64 are inserted into the holes 66 at a distance apart from each other, and fixed thereto. A pin-to-pin distance adjusting member 68 formed into a disk shape is secured to the extremity of the electrode pin 62 by resistance welding or the like. The pin-to-pin adjusting member 68 is disposed in a recess provided on the distal or front end surface of the header 54, so that the distal end surface of the header 54 around the recess and the pin-to-pin distance adjusting member 68 are flush with each other. The distal end surface of the pin 64 is disposed in flush with the distal end surface of the header 54. The structure of the pin-to-pin distance adjusting member 68 is not limited as long as it approaches the electrode pin 64, and may have a shape other than the disk shape.

In this embodiment, an integrated combination of the pins 62, 64, the pin-to-pin distance adjusting member 68, and the ceramic header 54 is manufactured in the following manner.

Binder and water are added to ceramic material powder which constitutes the header 54 as needed in advance. The pins 64, 62 with the pin-to-pin distance adjusting member 68 are disposed in a die for molding the header 54, and then the above-described material powder is filled therein and pressed to form a pressed powder member. Subsequently, it is dried, calcinated, and baked as needed. While the ceramic material powder may be fine ceramic material, china clay, clay and the like may be used as a main raw material. In the latter case, the baking temperature is on the order of 800 to 1300° C.

By this baking operation, a ceramic mold solidifies from the pressed powder member, and the outer peripheral surfaces of the pins 62, 64 and the ceramic header 54 are firmly integrated. In order to increase the connecting strength between the pins 62, 64 and the ceramics, it is possible to apply a glaze component on the outer peripheral surfaces of the pins 62, 64 in advance when forming the pressed powder member. While the glaze component may be sodium silicate, or sodium borosilicate which generate glass when sintered, for example, it is not limited thereto, and may also be glass powder.

After baking, the distal end surface of the header 54 is ground as needed, and ceramic components attached to the distal end surface of the pin-to-pin distance adjusting member 68 are removed.

The ceramic header 54 with the pins 62, 64 and the pin-to-pin distance adjusting member 68 integrated therewith may be manufactured by manufacturing a ceramic sintered body having the holes 66 in advance and inserting and fixing the pins 64, 62 with the pin-to-pin distance adjusting member 68 into the holes 66 on the ceramic mold. In order to perform this fixation, preferably, the pins 62, 64 applied with glaze on the outer peripheral surfaces thereof are inserted into the holes 66, then are heated to a temperature at which the glazing melts (for example, 400 to 900° C.) to melt the glazing, and then are cooled.

The bridge circuit line 70 is mounted between the pin-to-pin distance adjusting member 68 and the distal end surface of the pin 64. The bridge circuit line 70 is fixed using a technique such as welding or brazing.

The cup 52 has a shape to be fitted on the front half 58 and the rear half 60 of the header 54, and the rear end of the cup 52 is provided with a caulked portion 53 which is caulked along the rear end surface of the rear half 60 of the header 54. Part of the rear end surface of the rear half 60 is metalized, and one end of the metalized portion 72 comes into contact with the caulked portion 53, while the other end extends close to the electrode pin 62 so that static electricity can be discharged via the discharge gap between the other end and the electrode pin 62.

The cup 52 is formed with a tear line 52 a having a cross-shaped groove on the distal end surface thereof. A gasket 74 is disposed at a shouldered portion at the boundary between the front half 58 and the rear half 60 of the header 54.

In the initiator 50 constructed in such a manner, when a voltage is applied between the pins 62, 64, the bridge circuit line 70 is heated, whereby the reaction agent 48 starts reaction. Then, the tear line 52 a at the extremity of the cup 52 is torn by a gas pressure of gas generated by this reaction, and a high-temperature gas is discharged from the initiator 50. In the initiator 50 in this embodiment, the header 54 formed entirely of ceramic is employed, and hence the ceramic header 54 with the bridge circuit line 70 can easily be manufactured by forming the electrode pins 62, 64 integrally with the ceramic pressed powder member and then sintering the same, or by inserting the electrode pins 62, 64 into the ceramic mold with holes 66 and sealing the same.

In the present embodiment, part of the rear half 60 of the header 54 is metalized, one end of the metalized portion 72 comes into contact with the caulked portion 53, and the other end extends close to the electrode pin 62, so that static electricity can be discharged via the discharging gap between the other end and the electrode pin 62, whereby a static electricity discharging mechanism can be configured easily at a low cost. Even when static voltage is applied between the pins 62, 64 and the cup 52, erroneous ignition due to the spark of discharge is prevented by this discharging mechanism.

In the present embodiment, since the pin-to-pin distance adjusting member 68 is secured at the extremity of the pin 62, and the bridge circuit line 70 is connected to the pin-to-pin distance adjusting member 68, the distance between the pin-to-pin distance adjusting member 68 and the electrode pin 64 is small, and hence the length of the bridge circuit line 70 may be reduced. In addition, detachment of the pin 62 from the header 54 is prevented.

In an initiator 50A in FIG. 2, another pin-to-pin distance adjusting member 68 is fixed to the extremity of the pin 64 by resistance welding or the like, and the bridge circuit line 70 is mounted between the pin-to-pin distance adjusting members 68, 68. The rear end surface of a rear half 60A of a header 54A protrudes in a cylindrical shape as shown. Part of the rear half 60A is metalized, and one end of a metalized portion 72A comes into contact with the caulked portion 53, while the other end extends to a position close to the electrode pin 62, so that static electricity can be discharged via the discharge gap between the other end and the electrode pin 62. Other configurations are the same as the initiator 50 in FIG. 1, and the same reference numerals represent the same parts.

In the initiator 50A, since the pin-to-pin distance adjusting members 68 with larger diameters than the holes 66 on the header 54 are provided at the respective extremities of the pins 62, 64, the distance between the pin-to-pin distance adjusting members 68 is small, and hence the length of the bridge circuit line 70 may be reduced. In addition, detachment of the pins 62, 64 from the header 54 is reliably prevented.

An initiator 50B in FIG. 3 is tapered with the diameter of the intermediate portion of a rear half 60B of a header 54B decreasing toward the rear. The rear end portion of the front half 58 of the header 54B is formed with a recess 58 a for disposing the gasket 74. A cup 52A has a shape to be fitted on the header 54B, and the rear end thereof is formed with a caulked portion 53 caulked along the tapered portion of rear half 60B of the header 54B. Other aspects of this configuration are the same as the initiator 50 in FIG. 1, and the same reference numerals represent the same parts. While the pin-to-pin distance adjusting member 68 is provided only on the pin 62 in this embodiment, a pin-to-pin distance adjusting member 68 may be provided at the extremity of the pin 64 as well.

In the initiator 50B, since the rear end of the cup 52A is caulked along the tapered portion of the rear half 60B of the header 54B, the amount of deformation in association with caulking of the cup 52A, so that caulking can easily be performed.

In an initiator 50C in FIG. 4, the extremities of rod-shaped pins 62A, 64A are bent toward each other and substantially in an L shape. The bridge circuit line 70 is mounted between both of the extremities of the pins 62A, 64A.

Along the length of the pin 62A, a projection 62 a is formed in a branch shape, as shown. The projection 62 a is disposed so as to face the outer peripheral surface of the front half 58 of the header 54B. The extremity of the projection 62 a is disposed at a position slightly set back from the outer peripheral surface of the front half 58, and a small discharge gap is defined between the extremity of the projection 62 a and the inner peripheral surface of the cup 52A. The metalized portion 72A is not necessarily provided in this embodiment.

Other aspects of this configuration are the same as the initiator 50B in FIG. 3, and the same reference numerals represent the same parts. In order to manufacture the header 54B including the pins 62A, 64A integrated therewith, for example, it is preferable to apply a glassy glaze to the portions of the pins 62A, 64A coming into contact with the header 54B in advance, form and mold a ceramic material powder member together with the pins 62A, 64A, and then sinter the molded powder member.

In the initiator 50C, when static voltage is applied to the cup 52A, electric discharge occurs between the projection 62 a and the cup 52A. This static electricity discharging mechanism can be manufactured easily at a low cost.

In the present embodiment, the distance between the pins 62A, 64A can be reduced and the length of the bridge circuit line 70 can be reduced without welding the pin-to-pin distance adjusting members 68 to the extremities of the pins 62A, 64A, and the pins 62A, 64A can reliably be prevented from coming off from the header 54B.

An initiator 50D shown in FIG. 5 employs pins 62B, 64B bent into substantially a crank shape as electrode pins.

The pins 62B, 64B are disposed so that the distance between the front end sides is smaller than the distance between the rear end sides thereof.

As in the case of the pin 62A in FIG. 4(b), a projection 62 a protrudes from along the length of one pin 62B, and a discharge gap is defined between the extremity of the projection 62 a and the inner peripheral surface of a cup 52B. A gasket 74 a is disposed in the recess 58 a of the header 54B. A caulked portion 53 a at the rear end of the cup 52B engages the recess 58 a. In addition, a ring 76 is fitted on the caulked portion 53 a. Other aspects of the configuration are the same as the initiator 50C in FIG. 4 and the same reference numerals represent the same parts.

In the initiator 50D thus configured, since the pins 62B, 64B are formed substantially into a crank shape, and the extremities thereof are close to each other, the distance between the extremities of the pins 62B, 64B are reduced, and the bridge circuit line 70 can be mounted between them without using a pin-to-pin distance adjusting member 68. Since the pins 62B, 64B are bent, the pins 62B, 64B can not easily detach from the header 54B.

In this embodiment, since the caulked portion 53 a of the cup 52B is firmly retained in the recess 58 a by the ring 76, the cup 52B is prevented from coming off the header 54B. Also, since the gasket 74 a is firmly pressed by the ring 76 via the caulked portion 53 a, sealing property between the cup 52B and the header 54B is good.

In the present invention, an insulation layer may be provided on the inner surface of the metallic cup 52B as needed.

FIG. 7 shows an example in which an electrical insulation layer 52 i is provided on the portion of the inner surface of the cup 52 coming into contact with the reaction agent 48, and coming into contact with the front peripheral surface of the header 54.

FIG. 7 is provided with the insulation layer 52 i in the embodiment shown in FIG. 1, and it is also possible to provide the insulation layer 52 i in the same manner in other embodiments as well. While the insulation layer 52 i may be formed, for example, by coating an insulation coating compound, thermal-spraying an insulative ceramic, oxidation treating on the inner surface of the cup, etc., the method of formation is not limited thereto.

The above-described embodiments are examples of the present invention, and the present invention may take the form other than those shown in the drawings. For example, a thin spacer formed of dielectric material may be interposed in the air gap between the projection 62 a and the cup 52A or 52B.

The initiator of the present invention can be applied to various gas generators. The gas generators may be built in various airbag apparatuses for a driver's seat, a front passenger's seat, a rear passenger's seat, and for protecting the side, the head, and pedestrians, or for a seat belt tensioner.

For example, as shown in FIG. 8, the initiator may be employed in a gas generator 110 positioned in an airbag device 90 including an inflatable airbag 100. Further by way of example, as shown in FIG. 9, the initiator may be employed in a gas generator 190 that is positioned in a seat belt retractor 170 for driving a spool 180 for pretensioning a seat belt 130. U.S. Pat. No. 6,363,722 (incorporated herein by reference) discloses an exemplary retractor. The seat belt retractor 170 may be part of a seat belt apparatus 120 which may additionally include a seat belt 130, a shoulder support 140, a tongue 150, and a buckle 160. The present invention also includes providing the improved initiator and gas generator in other known seat belt pretensioners.

The priority applications, Japanese Patent Application No. 2003-206317, filed Aug. 6, 2003, including the specification, drawings, claims and abstract, and Japanese Patent Application 2004-57760, filed Mar. 2, 2004, including the specification, drawings, claims and abstract, are incorporated herein by reference in their entirety.

Given the disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims. 

1. An initiator comprising: a header substantially formed of at least one of ceramic and resin; a pair of electrode pins disposed through the header and having extremities facing a front end of the header; a bridge circuit line provided between the extremities of the electrode pins; a reaction agent configured to react upon being heated by the bridge circuit line; and a cup surrounding the reaction agent and a side surface of the header.
 2. The initiator according to claim 1, wherein the cup is formed substantially of metal and is fixed to the header by caulking.
 3. The initiator according to claim 2, further comprising an insulating layer formed on an inner surface of the cup.
 4. The initiator according to claim 2, wherein at least one of the electrode pins is disposed sufficiently close to the cup to thereby create a discharge gap across which static electricity may be discharged.
 5. The initiator according to claim 4, wherein said at least one of the electrode pins comprises a projection that protrudes from along a length of the electrode pin in a direction toward the cup so that the discharge gap is formed between the projection and the cup.
 6. The initiator according to claim 2, wherein part of the header is metalized to form a metalized portion, and one end of the metalized portion is in contact with the cup, and another end of the metalized portion extends to a position close to one of the electrode pins, so that static electricity may be discharged via a discharge gap between said another end and said one of the electrode pins.
 7. The initiator according to claim 1, further comprising a pin-to-pin distance adjusting member secured to the extremity of at least one of the electrode pins so as to approach the other of the electrode pins, wherein the bridge circuit line is connected to the pin-to-pin distance adjusting member.
 8. The initiator according to claim 1, wherein the extremities of the electrode pins are bent toward each other.
 9. The initiator according to claim 8, wherein each of said electrode pins has an L shape.
 10. The initiator according to claim 8, wherein each of said electrode pins has a crank shape.
 11. A gas generator, comprising: a gas generating agent; and an initiator coupled to and configured to ignite the gas generating agent, wherein the initiator includes a header substantially formed of at least one of ceramic and resin; a pair of electrode pins disposed through the header and having extremities facing a front end of the header; a bridge circuit line provided between the extremities of the electrode pins; a reaction agent configured to react upon being heated by the bridge circuit line; and a cup surrounding the reaction agent and a side surface of the header.
 12. An air bag device, comprising: an air bag; a gas generating agent configured to inflate the air bag upon ignition; and an initiator coupled to and configured to ignite the gas generating agent; wherein the initiator includes a header substantially formed of at least one of ceramic and resin; a pair of electrode pins disposed through the header and having extremities facing a front end of the header; a bridge circuit line provided between the extremities of the electrode pins; a reaction agent configured to react upon being heated by the bridge circuit line; and a cup surrounding the reaction agent and a side surface of the header.
 13. A seat belt device, comprising: a seat belt; a pretensioner connected to the seat belt; a gas generating agent configured cause the pretensioner to tension the seat belt upon ignition; and an initiator coupled to and configured to ignite the gas generating agent; wherein the initiator includes a header substantially formed of at least one of ceramic and resin; a pair of electrode pins disposed through the header and having extremities facing a front end of the header; a bridge circuit line provided between the extremities of the electrode pins; a reaction agent configured to react upon being heated by the bridge circuit line; and a cup surrounding the reaction agent and a side surface of the header. 